The establishment of desired orientational relationships of surfaces and structure components both to one another and to the vertical and horizontal is an important aspect of the construction industry. This aspect commonly includes the establishment of reference lines and planes having a desired orientation followed by the alignment of surfaces or structure components to such reference lines and planes. Therefore, in fulfilling this aspect of the construction industry, it is desirable to have a tool that quickly, easily and accurately establishes a variety of reference lines and planes in such a way that surfaces and structure components can be quickly, easily and accurately aligned with the reference lines and planes established.
In the prior art, various tools directed toward meeting this need have been developed. These tools include hand-held apparatus such as carpenter's squares, bubble levels and plumb bobs. Although reference lines may be quickly established using such hand tools, the length of such lines are limited by the physical size of such tools. As a result, accurate alignment of surfaces and structure components even slightly remote from such tools is difficult, if not impossible. In addition, the variety of reference lines provided by such tools is often limited: for example, a plumb bob can establish only a vertical reference line; most bubble levels can establish only a vertical reference line, a horizontal reference line and a reference line 45.degree. to the horizontal, most carpenter's squares can establish only a reference line perpendicular to another line.
Also included in the prior art are more complex devices such as theodolites, including the well-known surveyor's transit. Unlike the previously identified hand tools, theodolites are capable of establishing reference lines of relatively substantial length such that surfaces and structure components can be accurately aligned to such reference lines. Both the establishment of the reference lines and the alignment of surfaces and structure components to such reference lines, however, are fairly difficult and time consuming. Establishment of the reference lines includes careful positioning of a tripod and adjustment of several screw-type knobs to establish level. Then, two operators are needed to align objects along the reference line: one operator must be positioned at the theodolite or transit to view the reference line by sighting through the telescope of the theodolite, and a second operator must physically align the object in accordance with the first operator's instructions. Furthermore, theodolites are capable of establishing only a single reference line at a time. Thus, a reference plane can be established only approximately by establishing and marking a series of reference lines a single line at a time. Such marking is commonly accomplished through the use of stakes with string tied between them.
More recently, tools capable of providing optical outputs in the form of beams of light have been developed in the prior art. These tools often have adjustment devices and direction indicators such as level bubble vials and angular graduations so that the orientation of the beam or beams can be set as desired. Furthermore, the beam is generally provided by a laser since laser beams can be produced to have high coherence, low divergence and high intensity over relatively long distances. Thus, these tools offer advantages over theodolites in that they provide a well-defined reference line that can be received and interpreted at relatively large distances from the laser itself. Because of this remote indication capability, alignment of objects with the beam does not require an operator at the laser itself. Instead, a remote operator can align an object with the reference line established by the beam merely by moving the object until the beam strikes the object at the desired location. Furthermore, multiple reference lines having a desired relationship to one another can be established simultaneously using beamsplitters. Similarly, reference planes can be established using rotating reflectors. Various lasers developed heretofore for use in establishing reference lines and planes are shown in U.S. Pat. Nos. 3,528,748 issued Sept. 15, 1970, to Burch et al; 3,588,249 issued June 28, 1971, to Studebaker; 3,813,170 issued May 28, 1974, to Sears; and 3,897,637 issued Aug. 5, 1975, to Genho.
Burch et al shows the use of a double imaging system for aligning a laser beam after it has been focused on a target. Burch also shows the use of photoelectric methods for determining the position of laser beams with respect to a target.
Studebaker shows the use of a laser beam for automatically controlling grading level of an earth grader through the use of photosensitive target in combination with a servomechanism for controlling the flow of hydraulic fluid. The photosensitive target includes two vertically spaced photocells with a neutral zone in the space between the photocells. Studebaker also shows reflecting a vertical laser beam using a rotating pentaprism for establishing a horizontal reference plane. In addition, Studebaker shows reflecting a horizontal beam using a 45.degree. rotating reflector for establishing a vertical reference plane. Studebaker further shows a means for adjustably mounting a laser in a substantially vertical position. The laser is permanently secured to a tripod by means of a ball-and-socket joint. Level adjustments are made by screw means with bubble vials as a reference. The bubble vials are adjustable with respect to the laser so that a reference plane having a desired angular relationship to the grade can be established by adjusting a micrometer. Fine elevation adjustments are made by means of a rotatable spur gear cooperating with a rack gear.
Sears shows splitting the laser beam using one or more apertured 45.degree. reflectors. One of the resulting beams is used for positioning the laser device over a reference point on the ground. Sears also shows the use of two horizontal reference beams whose angular relationship is fixed by the design of the particular device. In addition, Sears shows gear means for manually adjusting the horizontal beams simultaneously to different directions within a horizontal plane.
Genho shows the use of a reflective-transmittive 45.degree. beamsplitters for transmitting either two or three orthagonal beams that can be used for squaring, leveling and plumbing. Genho also shows means for changing the position of one of the beams from horizontal to vertical by rotating the laser housing with respect to an adjustable support means. The support means includes two feet separately, threadedly mounted in a block that is rotatably and translatably attached to the housing. Genho also shows the use of a detachable rotatable reflecting pentaprism for establishing either a horizontal or a vertical reference plane.
While the prior art shows such tools capable of providing simultaneously a plurality of reference lines having a desired relationship to one another and of providing a reference plane having a desired orientation, none of the prior art shows a device that can be placed on any reasonably flat, substantially horizontal surface so as to provide a substantial selectable variety of reference lines and planes without requiring either substantial initial manual adjustment and leveling or substantial releveling and repositioning of the device when changing from one line or plane or set of lines and/or planes to another set of lines and/or planes. Such a device is desirable since it enables the performance of a wide variety of alignment functions and related activities while the device remains accurately positioned over a single reference point without any time consuming readjustments and releveling. Furthermore, such a device is desirable since, by providing a plurality of reference planes, it can be used to control the total operation of a piece of construction equipment.